Manufacture of insulation material



Examir 106. COMPOSITIONS,

Cross Reference COATING on PLASTIC. 86

Sept. 13, 1938. J. c. KERSHAW f 4 MANUFACTURE OF INSULATION MATERIAL I Filed Feb. 28, 1936 Qua/nu;

Patented Sept. 13, 1938 UNITED STATES PATENT OFFICE MANUFACTURE OF INSULATION MATERIAL John Clayton Kershaw,

Joplin, Mo., asslgnor to The Eagle-Picher Lead Company, Cincinnati,

hi0, a corporation oi Ohio Application February 28, 1936, Serial No. 66,306

11 Claims.

The invention relates to a new and improved e t in ul tin m teriai and method of producmg ame rea y W1 hstands high temperatures without disintegration. The invention comprises the addition of materials to a mix in definite proportions and under given operating conditions whereby a product of the desired quality can be produced in an eflicient and economical operation.

It is an object of the invention to provide a method for producing a heat insulating material having low density and low thermal conductivity at high temperature ranges.

Another object of the invention is the. provision of a method for producing a thermal insulating material which can be molded into blocks and shapes with a density varying from 16 to pounds per cubic foot.

Another object of the invention is the produc- 20 tion oi an insulating material which can be molded into blocks and shapes of low density and high insulating efilciency as compared with similar articles manufactured and sold at the present time 5 A iurther object 0! the invention is the provision of a continuous step by step method 01' producing heat insulating material which can be molded into blocks and shapes of low density and having low thermal conductivity at high tempergo ature ranges.

Further'objects are to provide a method of maximum simplicity, efiiciency, economy, ease oi operation and assembly and such further objects, advantages and capabilities as will later more 5 fully appear, and are inherently possessed thereby.

The invention further resides in the combination of steps, construction and arrangement illustrated in the accompanying drawing, and where 4 I have shown'a preferred embodiment it is to be understood that the same is susceptible of modification and change, and comprehends other details, arrangement of parts, methods, features and constructions without departing from the 45 spirit of my invention.

Figure 1 is a diagrammatical illustration showing apparatus constructed in accordance with the invention. With reference to the disclosures in the drawing the invention briefly comprises an a conventional digester into which materials to be treated are introduced in the presence of a fixed volume of air and a fixed volume of water and thoroughly agitated for a fixed period of time, when the discharge outlet is opened and 55 the digested material and liquid are removed through a conduit by pressure sufllcient to force both material and liquid into a mold, where it is formed into blocks and shapes and further treated to cure and dry the finished product.

Figure l is a blow fan of conventional design the blades of which can be used to disperse cercurely connected with both conduit 3 and inlet 5 to form a continuation of conduit I and removed at will to form ready access with the interior of digester 6. Inlet 5 is of a size that will permit ready access of materials into digester 6 by pouring or shovelling and so constructed that it can be readily sealed with an air-tight covering such as a conventional type boiler manhole cover to prevent the passage of air into or from digester 6. l is a discharge outlet by means of which material from the digester 6 is passed through con-- duit 8 into the molds 9, while I 0 is an outlet valve which can be opened or closed at will and controls the dew of materials through conduit 8 into the molds 9 of any desired size and shape. Air from a compression tank (not shown) is fed by means of the line H into digester 6 through inlet it. The inlet I2 is located in spaced relationship to the bottom of the digester 6 so that air entering under pressure will act on materials at the lowest point and keep the entire contents in a state or suspension, while maintaining static pressure in the static pressure area 2! when desired. I3 is an intake valve which can be opened and closed at will and serves to admit the air supply flowing through the line H and out the inlet l2. I4 is an outlet designed to permit the escape of pressure through the control valve I5 and, conduit it into the open air. Pressure gauges ll attached to conduit 8 and digester 6 are of conventional design. I8 is a recording air fiow meter for indicating the volume of air passing through inlet l2 and thence through the mixture. i9 is a controlled valve for controlling the static pressure above the mixture and is operated by a pressure controller 20. 2| is the static pressure area in digester 6 and 22 is the mixture area. 23 is a stationary support or foundation for digester 6.

The invention consists principally in preparing what I call the raw material by introducing the different ingredients into digester 6 in regulated quantities in the presence of air and a fixed volume of liquid and agitating same by means of 5 compressed air until the mass is thoroughly digested. In practice I fill digester 6 with a fixed volume of 1i uid and inject air under pressure through inle I! sufllcimm tation. Asbestos fiber is um memto fine shreds to reduce the density by coming in contact with the revolving blades while leaving fibers long enough to give the desired tensile strength. It is then passed by means of pressure from the fan, through conduit I and duct 4 to digester 6 while the liquid is in a state of violent agitation. The fibers should be passed through the fan and into the digester at an even and constant rate to prevent bunching and formation of tufts which otherwise 30 tends to lower the tensile strength. Magnesium oxide is then introduced by pouring roug care being exercised to make certain that it is evenly distributed and thoroughly broken up by agitation. There is then added magnesium sulhate by the same method an e w Fhoroughly agitated until such time as a preliminary formation of what I call ma esium oxysulphate c'r stals is in progress. figm- We vermiculite of desired size and density and c'onti'nue agitation of the whole mass for a leng o e necess y to reach maximum distribution of the ingredients. By this means my raw material is efllciently and economically formed, being of a nature which can be readily molded into blocks and shapes that upon further treatment will give the desired density and tensile strength.

The invention further consists in forcing the raw material so prepared from the digester into a 40 mold of desired shape and size where part of the water originally present in the mix is forced out and the molded shape removed from the form to be kept at a constant temperature for a period of time sufiicient to permit the growth of formed oxysulphate crystals at controlled temperatures. At the end of this period the blocks and shapes are placed in an oven where the remaining water is expelled and the material is then ready for machining to the desired finished dimensions.

Without desiring to restrict myself to the proportions named I will give an example of the method for carrying out my process which will possess the advantages described." It will be understood the amounts given are approximate 66 only and that the relative proportions of material may be varied to a reasonable extent without impairing the results. Y

Into digester 6 containing 465 gallons of water air is injected through inlet i2 at the rate 0!. about 200 cubic feet per minute sufiicient to pro-' vide violent agitation of the water and the ingredients to be added In the example given the air has a pressure of 80 pounds per square inch. A bestos fiber with a screen analysis of 2-8-4-2 mm the blow fan I where it is dispersed by the blades to reduce the. density from approximately 11.25 lbs. to 7.75 lbs. per cubic foot at atmospheric pressure, leaving fibers long 0 enough to give the desired tensile strength. The

fibers thus prepared are passed by means of pressure from the blow fan through conduit 3, duct 4, and inlet 5 into digester 6 in an amount equal to u 35 pounds by weight, it being necessary to add the fibers at an. even rate to prevent bunching and the formation of tufts which tends to lower the tensile strength of the finished product.

I next add pounds of magnesium oxide by weight to digester 6 by pouring same a an en rate through inlet 5 and continue agitation until it is thoroughly broken up, after which I add 50 pounds of magesium sulphate in the same manner and erea 1' con inue agitation of the entire mass for approximately one hour and fortyfiveminutes during which time a chemicalreaction is started that results in the formation of what I call magnesium ox sulphate cr stals By this step in the operation I provide a one ical bond which forms the cementing action for my product. I next introduce in the same manner 305 pounds of exfoliated vermiculite with a screen size before e a ion 0 m1 us 28 and continue agitation for approximately 15 minutes to provide maximum distribution. The resulting product comprises my raw material and is a semi-fluid mix comprising water, asbestos fibers, magnesium oxysulphate crystals and exfoliated vermiculite in which the weight of the water equals approximately eight times the weight of the solids.

To carry out the molding operation the digester is sealed and a static pressure of 15 to 20 pounds per square inch provided. The discharge outlet 1 is then opened by turning control valve in permitting the raw material in the digester to be forced under static pressure through conduit 8 into molds 9, where approximately 5 parts by weight of the water originally present in the mix along with a certain proportion of the formed oxysulphate crystals are squeezed out. The molded form is removed from the molds and maintained at a temperature of approximately 70 degrees Fahrenheit for 48 hours when it is placed in an oven for drying at a temperature not to exceed 300 degrees Fahrenheit. Upon completion of this latter operation my heat insulating material in the form of molded shapes and blocks is ready for machining by conventional methods to finished dimensions.

It may be said that agitation is continued from the first introduction of dispersed fibers into the digester until completion of the molding operation. During the latter period agitation is necessary as otherwise the pressure tends to filter out the liquids through the solids, causing the latter to settle in the bottom of the tank by reason of the varying densities of the diiferent ingredients that comprise the raw material. In particular it should be pointed out that my process depends upon simultaneously maintaining a controlled agitation and a controlled static pressure during the molding operation, and this I successfully accomplish by the use of inlet valve l3, the outlet valve IS, the air flow meter l8, the control valve l9, and the pressure controller 20.

To illustrate one method by which I maintain this continuously controlled agitation and static pressure during the molding period, the tank is first sealed and the static pressure controller 20 is set for a pressure of approximately 20 pounds,

which, when the intake valve I3 is completely opened, operates the control valve l9, permitting a pressure of 20 pounds to build up in the static pressure area 2 I. This volume of air is measured by the air flow meter i8 and passes through the intake I2 and thence through the mixture 22."

By manipulation of outlet valve I5 and observation of the air flow meter l8, a given volume of air passes thus through the mixture, the control valve l9 permitting this passage when sufficient air has been discharged from the static pressure 106. COMPOSITIONS,

COATING OR PLASTIC.

area 2| to reduce this static pressure below that for which the pressure controller 20 has been set. The volume of air necessary to maintain proper agitation in this illustration is approximately cubic feet per minute. Regardless of the initial air pressure, this flow is constantly maintained by this method.

While I have described the use of a blow fan to shred and feed asbestos fibers and other ingredients into digester 6, it is to be understood the same is by no means necessary to the successful carrying out of the operation, as other methods equally effective may be used, as for instance by pouring or feeding the ingredients in by hand or from an overhead hopper.

It is a characteristic of my material that it can be forced under pressure into the molds and there formed into blocks and shapes without substantial setting of the ingredients in the semi-fluid mix by chemical reaction. The cementing action of the magnesium oxysulphate crystals progresses slowly and evenly throughout the entire molded shape for the 48 hour waiting period while it attains the high tensile strength desired. Likewise in the drying operation care must be exercised that the oven temperature does not exceed 300 degrees Fahrenheit over a sustained period, as otherwise the cementing action of the oxy phate crystals is destroyed.

By the foregoing operation I am enabled to prepare an insulating material with a density varying from 16 to 20 pounds per cubic foot and with low thermal conductivity, capable of withstanding high temperatures without disintegration. My finishe contains approximately the folowmg ngre en s:

Per cent Asbestos fibers 7 esium oxysulphate crystals 32 Exfoliated vermiculite 61 Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The herein described process of producing a binder for the manufacture of heat insulation which comprises adding finely divided asbestos fibers to a fixed volume of water and agitating same, adding magnesium oxide'and continuing agitation until thoroughly dispersed, adding magnesium sulphate and continuing agitation of the entire mass for approximately one hour and forty-five minutes to produce a preliminary formation of magnesium oxysulphate crystals by chemical reaction.

2. The herein described process of producing raw material for the manufacture of heat insulation which comprises adding finely divided asbestos fibers to a fixed volume of water and agitat-ing same, adding magnesium oxide and continuing agitation until thoroughly dispersed, adding magnesium sulphate and continuing agitat on of the entire mass for approximately one hour and forty-five minutes to produce a preliminary formation of magnesium oxysulphate crystals by chemical reaction, introducing exfoliated vermiculite and continuing agitation of the entire mass for approximately 15 minutes.

3. The herein described process of preserving the cementing action of formed magnesium oxysulphate crystals which comprises forming the oxysulphate crystals in a preliminary state of formation, incorporating the same into a formedobject and permitting the object to stand at a constant temperature of approximately 70 detress Reference grees Fahrenheit for 48 hours to permit the growth of formed oxysulphate crystals, and completing the process by drying at a temperature not to exceed 300 degrees Fahrenheit.

4. The improvement in the process of manufacturing heat insulating material which comprises forming asbestos fibers, magnesium oxide, magnesium sulphate and exfoliated vermiculite into a semi-fluid mass containing oxysulphate crystals in a preliminary state of formation, forcing the same into molds under pressure, removing the formed shape from the mold and maintaining same at a constant temperature to permit the growth of oxysulphate crystals and a substantial setting of the ingredients by chemical reaction, and completing the operation by drying at a temperature which will preserve the cementing action of the formed oxysulphate crystals.

5. The improvement in the process of manufacturing heat insulating material which comprises forming asbestos fibers, magnesium oxide, magnesium sulphate, and exfoliated vermiculite into a semi-fluid mass containing oxysulphate crystals in a preliminary state of formation, forcing the same into molds under static pressure of 15 to 20 pounds per square inch, removing the formed shape from the mold and maintaining at a constant temperature of approximately 70 degrees Fahrenheit for 48 hours to permit the growth 01'. formed oxysulphate crystals, and completing the process by drying at a temperature not to exceed 300 degrees Fahrenheit.

6. The improvement in the process of manufacturing heat insulating material which comprises forming magnesium oxysulphate crystals in the presence of asbestos fibers and water maintained in a constant state of agitation, adding exfoliated vermiculite and digesting until the mass is semi-fluid, forcing the same into molds under static pressure, removing the formed shape from the molds and maintaining same at a constant temperature of approximately 70 degrees heat insulating material comprising the steps of introducing a fixed volume of liquid into a digester and agitating same by means of compressed air, adding finely divided asbestos fibers, adding magnesium oxide and digesting, adding magnesium sulphate and digesting, and continuing agitation of the entire mass for approximately one hour and forty-five minutes, introducing exfoliated vermiculite and continuing agitation for approximately 15 minutes.

8. The step by step process of manufacturing heat insulating material comprising the steps of introducing a fixed volume of liquid into a digester and agitating same by means of compressed air, adding finely divided asbestos fibers,- adding magnesium oxide and digesting, adding magnesium sulphate and digesting, and continuing agitation of the entire mass for approximately one hour and forty-five minutes, introducing exfoliated vermiculite and continuing agitation for approximately 15 minutes, forcing the raw material thus formed under static pressure from the digester into molds, removing the molded form from the mold and maintaining same at a temperature of approximately 70 degrees Fahrenheit for 48 hours and placing the same in an Examim 9. The step by step process 01' manufacturing heat insulating material comprising the steps of introducing 465 gallons of water into a digester and agitating same by means of compressed air same in an oven for drying at a temperature not to exceed 300 degrees Fahrenheit.

10. In the manufacture of heat insulating material the step which comprises introducing magnesium oxide in the presence of a fixed volume oi.

5 with a pressure of 80 pounds per square inch, and

while agitation is continued adding asbestos fibers water and asbestos fibers agitated by compressed with a density oi. approximately 7.75 lbs. at atair and agitating the mass until magnesium oxide mospheric pressure, adding 110 pounds of magis thoroughly dispersed and adding magnesium nesium oxide and digesting, adding 50 pounds of sulphate and continuing agitation of the entire magnesium sulphate and digesting and continumass for approximately one hour and forty-five l0 ing agitation of the entire mass for approximinutes to produce a preliminary formation of mately one hour and forty-five minutes, intromagnesium oxysulphate crystals. ducing 305 pounds of exfoliated vermiculite and 11. Heat insulating material with a density of continuing agitation for approximately 'min- 16 to 20 pounds per cubic foot and low thermal 15 utes, forcing the raw material from the digester conductivity comprising asbestos fibers 7%, mag- 15 under static pressure into molds, removing the molded form from the mold and maintaining same at a temperature of approximately degrees Fahrenheit for 48 hours and placing the nesium oxysulphate crystals 32 and exfoliated vermiculite 61%.

JOHN CLAYTON KERSHAW. 

